Scorecard for Hospitalization After Outpatient Surgery

PHILADELPHIA, March 19 -- There's a checklist for prospective surgical outpatients who are the most likely to wind up being surgical inpatients.

The list includes outpatient surgical patients who are older, scheduled for longer surgery, who will have regional or general anesthesia, or have one or more of five comorbidities, according to researchers here.

Patients with at least four of the risk factors were more than 30 times more likely to require hospitalization than those with one risk factor or none, reported Lee A. Fleisher, M.D., of the University of Pennsylvania, and colleagues in the March issue of the Archives of Surgery.

Determining the risk score preoperatively may help clinicians and patients decide on the most appropriate setting for a procedure, they said

"This is not to suggest that patients with an outpatient surgery admission index of four or higher should universally undergo inpatient surgery," they wrote, "rather, clinicians should consider performing surgery on these patients in a setting where there is additional medical support to treat acute adverse events and to permit rapid transfer to an inpatient hospital."

The study included 783,539 procedures at hospital-based and freestanding ambulatory surgery centers in New York during 1997, recorded in an Agency for Healthcare Research and Quality database.

The researchers excluded cardiac catheterizations, endoscopies, cataract operations, and discharges other than routine or short-term hospitalization.

Most procedures were done in a hospital-based facility (95%). Most patients were young or middle-age (57.0% women, 65.5% age 19 to 64). General anesthesia was used in 35.9% of cases. Operative time was one to two hours for 31.3% of the procedures and longer than two hours for 10.1%.

The researchers divided the patients randomly into an analysis group and a group that was used to validate the risk scoring index. The findings were:

• In the overall group, 0.4% were discharged directly for short-term.
• hospitalization (one in 180) and 19 died during their procedure (one in 41,240).
• In the analysis group, 0.6% were discharged directly for short-term hospitalization and eight died during their procedure (one in 49,012).

Independent risk factors were assigned points for the risk score index. The factors were:

• 65 or older (odds ratio 1.58, 95% confidence interval 1.42 to 1.77, 1 point),
• Operating time longer than two hours (OR 4.34, 95% CI 3.86 to 4.88, 1 point),
• Cardiac diagnoses (OR 0.74, 95% CI 0.53 to 1.04, 1 point),
• Peripheral vascular disease (OR 3.15, 95% CI 1.89 to 5.23, 1 point),
• Cerebrovascular disease (OR 3.73, 95% CI 1.83 to 7.64, 1 point),
• Malignancy (OR 1.62, 95% CI 1.42 to 1.85, 1 point),
• HIV seropositive (OR 2.33, 95% CI 1.09 to 4.96, 1 point),
• Regional anesthesia (OR 1.53, 95% CI 1.12 to 2.10, 1 point), and
• General anesthesia (OR 11.94, 95% CI 10.41 to 13.70, 2 points).

While cardiac diagnoses were not significantly linked to increased risk of admission, it was included "based on a prior belief that this is an established clinical risk factor," Dr. Fleisher and colleagues wrote.

Those who had more of the risk factors were at increasingly higher risk for hospital admission immediately after their procedure. Compared to patients with a score of zero or one, the findings were:

• Scores of four points or higher (2.8% of the sample) were linked to 31.96-fold higher odds of hospitalization (95% CI 26.29 to 38.86) with 2.8% of these patients discharged to the hospital,
• A score of three points (9.1% of the sample) increased the odds 20.60-fold (95% CI 17.56 to 24.18) with 18.3% of these patients being hospitalized,
• A score of two points increased the odds 9.50-fold (95% CI 8.16 to 11.05) with 8.5% being hospitalized, and
• Odds ratios similarly increased with index scores for the validation group.

However, the researchers noted that because there was a low absolute rate of hospitalization, a substantial increase in odds ratio represents a low proportion of cases.

"Consequently, the number of false-positive findings require this model to be a supplement to clinical judgment, suggesting cases where a higher level of evidence concerning the safety of ambulatory surgery is appropriate," they wrote.

They also cautioned that there was no data the patients' presurgical situation or whether some of the admissions were planned. Prospective studies using the index developed by the researchers may be needed to address these issues, they added.

Furthermore, since most of the procedures were done in outpatient hospital settings, the findings may not reflect practice patterns or results for freestanding surgical centers.

"Surgery in locations distant from a hospital, such as freestanding ambulatory surgical centers or physicians' offices, might result in increased, avoidable morbidity or mortality, although such findings are difficult to demonstrate given our predominantly outpatient hospital data set," they wrote.

Outpatient surgery climbed from 16% of surgeries in 1980 to 50% in 1990 to about 63% in 2000 with a corresponding increase in the complexity and types of procedures done on an outpatient basis.

"Public health policy and corporate incentives have encouraged ambulatory surgery; its growth has been one of the most rapid and fundamental changes in medical care during the past 20 years," Dr. Fleisher and colleagues wrote.